Certain sunglass tint combinations can cause a marked decrease in color-deficient drivers ability to detect and recognize traffic signals, according to a study in the April issue of Optometry and Vision Science.

Individuals who demonstrate color vision deficiency (color blindness) often have difficulty interpreting red/green and blue/yellow coloration patternsthe same color combinations universally used in traffic lights. Sunglasses that feature comparably tinted lenses further inhibit these patients perception of red/green and blue/yellow combinations.

In this study, 20 normal patients and 49 color-deficient patients were asked to identify the color of simulated traffic signals while wearing clear, gray, green, yellow-green, yellow-brown or red-brown sunglasses.

Response times for color-deficient subjects were considerably slower than those of normal subjects when looking at both red and yellow signals, regardless of sunglass tint. And, many color-deficient subjects had trouble seeing red signals while wearing lenses that were tinted either red-brown or yellow-brown. Finally, most color-deficient subjects demonstrated minor difficulty recognizing yellow and green lights while wearing sunglasses with a yellow-green or green lens tint.

The authors concluded that individuals with color vision deficiency should avoid sunglass tint combinations that are similar to common traffic signal colors.

This study illustrates that certain sunglass tint combinations with particular color vision deficiencies will decrease a given patients reaction time due to color confusion, says Michael Mayers, O.D., of Powell, Ohio. This would be a valuable discussion for patients in my office with color blindness in order to assist them in selecting the best functional tint combination for their particular color deficiency.

Still, patients with color vision deficiency must wear sunglasses to protect their eyes from damaging ultraviolet rays, Dr. Mayers says. I recommend polarized gray sunglasses with UV protection for patients with color deficiencies because gray lenses filter the visible light spectrum equallyoffering the patient the benefits of sunglasses while minimizing color vision perception time.

Dain SJ, Wood JM, Atchison DA. Sunglasses, traffic signals and color vision deficiencies. Optom Vis Sci 2009 Apr; 86(4):e296-305.

Vol. No: 146:06Issue: 6/15/2009